CODEWITHSUNDEEP
javascriptnode.jsunit-testingjasmine
dilusha_dasanayaka
dilusha_dasanayaka

Reputation: 1441

Use jasmine spyOn with function

I need to write unit test cases in jasmine (& karma) for something like below. It uses rollup to compile it.

const A = () => {
 B();
}

const B = ()=> {
 console.log("B is called");
}

exports {A}

In here my test.js file, I need to check whether the B() is called, when we call A(). So I try something like this.

import * as mainFunctions from 'main.js'

describe("" , function() {
  beforeEach(()=> {
    spyOn(mainFunctions, 'B');
    A();
  });

  it("", function() {
    expect(mainFunctions.B).toHaveBeenCalled();
  });
});

But it gives me the error "Error: : B is not declared writable or has no setter" when I run the test. Please suggest me a method to overcome this.

Upvotes: 0

Views: 279

Answers (1)

Daniel
Daniel

Reputation: 2531

B is private for all intents and purposes (it's not exported) and you should not directly test private methods.

What you can test is the effect of A. We expect that when A is called console.log will trigger. So you can test the effect by spying on console.log.

console.log in this case is a module dependency. When writing Unit-Test you should mock (spy) on all used dependencies and call all the available public methods.

spyOn(console, 'log');

...

it('should print log to console', function(){
  mainFunctions.A();
  expect(console.log).toHaveBeenCalled();
})

Note: console should not be used directly (or mocked) in production. You should implement a LoggerService (see: winston) and spy on it instead.

Upvotes: 1

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